A box remains a flat sheet until the last moment.
Packaging is essentially a three-dimensional challenge, while printing is a two-dimensional process. Everything visible on a completed carton was initially printed flat. It was then cut, creased, folded, and glued. The document that links these two states is the dieline. Almost every packaging issue can be traced back to the dieline being incorrect, ignored, or drawn after the artwork instead of before.
This guide covers the basics of folding cartons: what a dieline is and how to work with one, how to choose the right board, and what considerations are necessary when artwork needs to survive the folding process. Additionally, the guide outlines the quality checks that prevent costly errors during the first run.
The dieline comes first
A dieline is a technical drawing of the flat carton, showing three types of lines: cut lines, crease lines, and glue areas. It is created based on the internal dimensions of what will go inside the box, along with allowances for the thickness of the board itself.
The sequence that works is: measure the product, produce the dieline, create a physical sample, and then finalize the design based on the confirmed dieline.
When you receive a dieline, it will typically arrive as a vector file with the lines on their own layer. Work on layers beneath it, never directly on the dieline layer, and never move it. When supplying your artwork, ensure the dieline layer remains present but is clearly marked as non-printing. This allows the die to be accurately checked against the design.
Board thickness changes the dimensions
This part is not immediately obvious. A box built to the exact dimensions of the product will not close, because the board has thickness, which accumulates at every fold. Allowances are built into the dieline for this, and they differ based on board weight. This is why a dieline drawn for a 300 gsm board cannot simply be reused for a 400 gsm board.
Choosing board
Cartons are specified by the type and weight of the board used, and this choice impacts the carton's appearance, strength, and cost.
- Folding boxboard: the general-purpose choice, usually white on the outside with a cream or grey inner. Good value, prints well, suits most retail packaging.
- Solid bleached board: white throughout, cleaner appearance on both faces, higher cost. Used where the inside of the box is visible or where a premium look matters.
- Kraft and recycled board: brown or grey, strongly associated with sustainable and artisan positioning. Colour reproduction is muted because the base is not white, which needs planning for at design stage.
- Corrugated: for shipping and heavier products. Print quality on standard corrugated is lower unless a litho-laminated construction is used.
Weight is typically measured in gsm (grams per square meter) or in microns. Heavier board is stiffer and more protective, but it is also harder to fold cleanly and more expensive to ship. For small, lightweight products, using heavy board is often unnecessary and wasteful.
Printing on unbleached board
If you are using kraft for its appearance, be prepared for how it affects colors. All inks applied over brown will result in earthy tones, and pale shades may vanish. Effective designs on kraft paper use minimal colors, strong contrasts, and often a single dark ink. Attempting to replicate a bright brand blue on kraft typically leads to disappointment unless a white underprint is added, which increases costs and somewhat undermines the desired look.
Designing for the folds
Artwork on packaging must withstand being creased and folded, which alters several rules:
- Keep detail away from creases. Text or fine detail crossing a fold will crack and break up. Leave clear space either side.
- Heavy ink coverage cracks. A solid dark colour folded across the grain will show a white line where the fibres split. Board grain direction matters, and your printer will orient the layout accordingly.
- Panels are not all equally visible. Work out how the box sits on a shelf and put the important content on the panel that faces out.
- Glue flaps must stay clear. Ink and varnish stop glue bonding. The dieline marks these areas, and they need to be free of coverage.
- Allow bleed on every outer edge. Cutting moves slightly, and a white sliver on a box edge is very visible.
- Tuck flaps need clearance. Anything printed on a flap that tucks inside will not be seen, so do not put required information there.
The cracking issue is the same one that affects any thick stock being folded, and the underlying mechanics are covered in the general guidance under print quality and materials.
Information that is required and content that is regulated
Packaging often needs to include mandatory information, which varies based on the product category and the market it is sold in. This information typically includes ingredients, allergens, weight, batch codes, country of origin, recycling symbols, barcodes, and minimum type sizes for certain elements.
Two practical points to consider. Firstly, establish these requirements before the design phase, not after. This matters because these elements take up space, and there is never as much space as you would expect.
Batch codes and date marks are usually applied after production rather than printed, so leave a clear, uncoated area for them. Where codes need to be printed and unique per unit, that is variable data work, covered under business printing.
Always make a physical sample
A flat proof on screen confirms that the artwork is correct. However, it does not indicate whether the box closes properly, if the product fits well with the packing material, if the flap tucks smoothly without buckling, or if the shelf-facing panel is the one intended.
Request a cut-and-folded sample made from the actual board material before finalizing your order. This step involves creating an actual product, closing it, opening it, and stacking two of them. This process incurs minimal cost and helps identify any failures that are only apparent in three-dimensional form.
Packaging work with us
We produce the dieline based on your product dimensions, rather than requiring you to supply one. We then send a folded, blank sample on the specified board prior to printing.
When a design features heavy coverage across folds, we will note this and suggest either a lighter build in that area or a different board orientation. For barcodes, we verify readability from a printed sample rather than assuming the file is correct.
Send us the product dimensions, the quantity and any mandatory content it has to carry, and we will come back with a dieline and a board recommendation. See related work under digital printing, or for short deadlines see express printing. Get in touch through the contact page.
The short version
Start by creating the dieline from the product first, and then design onto it, not the other way around. Choose the board based on the product's weight and the desired look, remembering that kraft board will mute every color. Keep details and heavy coverage away from creases, ensure glue flaps are clear of ink, and allow for bleed everywhere. Sort out the mandatory content early on, as it often requires more space than anticipated.
Then fold a real sample and place the actual product inside it. Screens do not close boxes.
